The proposed project will study insulin receptors and insulin action in cells isolated from normals, insulin resistant non diabetic subjects, subjects with NIDDM, and relatives as described in Project I. These studies aim to identify the cellular defects of insulin action in these individuals and correlate these defects with decreased insulin action in vivo. Insulin receptors will be examined in two freshly isolated cells adipocytes and monocytes, and two cultured cells, lectin-stimulated T virus-transformed B lymphocytes. The receptors in and on cells, the fraction of receptors on the cell surface, and the ability of cells to internalize the hormone will be measured. Both conventional ligand binding assays and a new insulin receptor radioimmunoassay will be employed. ln transformed B lymphocytes, the biosynthesis and turnover of the receptor, employing both I-labeled surface receptors and 35S-labeled total cellular receptors, will be measured. Also, insulin receptor mRNA will be quantitated. Insulin receptor kinase activity will be analyzed in B lymphocytes and monocytes. Insulin stimulated glucose transport will be measured in adipocytes, and insulin stimulated pyruvate kinase will be assayed in T lymphocytes. These studies will provide new data, therefore, on insulin receptors and insulin action in individuals with insulin resistance and NIDDM.